<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<script src="js/jquery-3.7.1.min.js" type="text/javascript" charset="utf-8"></script>
		<script type="text/javascript">
			$(function(){
				$("input").change(function(){
					$("input:eq(2)").attr("value",
						$("input:eq(0)").val()*1 + $("input:eq(1)").val()*1
					)
				})
			})
		</script>
	</head>
	<body>
		<input type="text" placeholder="第一个数">+
		<input type="text" placeholder="第二个数">=
		<input type="text" placeholder="计算结果" disabled="disabled">
	</body>
</html>
